Vertical cutter and method of use

ABSTRACT

A detachable vertical cutter for insertion into a cylinder or tube is formed as a single unitary structure. The single blade has a pair of tool attachment end portions and a cutting blade extending in a loop between the attachment ends. The cutting blade is inclined vertically relative to a longitudinal axis of a cylinder or tube into which the attachment ends can slide into. The cutting blade has a cutting edge, a portion of which when extended free of the cylinder or tube will extend a distance greater than the tube outside diameter. The cutting edge when pushed inwardly and pulled outwardly between adjacent vertebrae scrapes and cuts disc material. When retracted the cutting blade deflects into the cylinder or tube for insertion or extraction into or from the disc space.

TECHNICAL FIELD

The present invention relates to an improved tissue and bone surfacescraping and cutting device for preparation of the spinal disc space forimplantation of a fusion implant device.

BACKGROUND OF THE INVENTION

In open spinal vertebrae surgical procedures, the surgeon makes anincision through the skin and muscle tissue and exposes the area to beworked on using retractors separating the tissue above the adjacentvertebral bodies and the interposed disc. Using cutting devices such asa spoon curette or rongeur, the surgeon cuts away the bone and discmaterial and prepares a space for a spinal fusion device to be placed.

In minimal invasive surgery, the large incision is not used and in itsplace a smaller cut is made just large enough to position a small hollowtube or cylinder into the disc space between the two vertebrae to befused together. It is through this tube that the cutting tools must passto remove the disc material and prepare the space for a fusion implantdevice. The vast majority of these cutting devices operate by rotationalcutting of the tissue to be removed. This allows for a circular crosssectional removal of the disc, but requires rather difficult angulationto flatten or widen the space being prepared. A secondary issue is toflex into a tube fitting compressed size; the blades typically have twoor more separate cutting blades as in U.S. Pat. No. 5,709,697. Thisenables the blades to deflect into a tube, but uses a small pointy tipprone to break when in use leaving metal fragments.

Very importantly, these rotational devices are limited in vertical reachthat can be achieved. In some small patients, this represents littletrouble, but in larger boned patients, the vertical space required forthe implant can exceed the capacity of the device.

The present invention as described hereinafter avoids these issues in anew and improved way to provide the surgeon a much simpler and efficientway to prepare the disc space for implantation.

SUMMARY OF THE INVENTION

A vertical cutter for insertion into a cylinder or tube is formed as asingle unitary structure. The single blade has a pair of tool attachmentend portions and a cutting blade extending in a loop between theattachment ends. The cutting blade is inclined vertically relative to alongitudinal axis of a cylinder or tube into which the attachment endscan slide into. The cutting blade has a cutting edge, a portion of whichwhen extended free of the cylinder or tube will extend a distancegreater than the tube outside diameter. The cutting edge when pushedinwardly and pulled outwardly between adjacent vertebrae scrapes andcuts disc material. When retracted the cutting blade deflects into thecylinder or tube for insertion or extraction into or from the discspace.

The blade is cut from a flat sheet of shaped memory alloy and heat setto form the loop. The sheet has a nominal thickness of 0.5 mm orgreater. The cutting blade has a nominal width of 2.0 mm or greater. Thecutting edges are the inclined outer edges at the intersection of thethickness and the width. The cutting blade has curved opposing sidesspanning a nominal maximum width between opposite sides a distance of10.5 mm or greater.

The cutting blade when withdrawn into the tube or cylinder bends ordeflects the curved opposing sides of the cutting blade to fit theinside diameter. This also lowers or bends the flattened end verticalinclination to slide into the tube or cylinder. The cutting blade hasflattened distal end portion between the two curved sides along avertical cutting peak extending at least 3 mm. The cutting blade isconfigured to fit into a tube or cylinder having a nominal outsidediameter of 8 mm. The vertical inclination of the cutting blade extendsat least 2 mm or greater above the outside diameter of the tube when thecutting blade is extended free of the tube.

A vertical cutting tool has a shaft, a tube or cylinder and a singlecutting blade. The shaft has the cutting blade attached at one end andis externally threaded at an opposite end. This hollow tube or cylinderis for receiving the shaft internally. A rotatable knot is affixed tothe hollow tube and is rotatable independent of the tube or cylinder.The knob has internal threads to engage the threads of the shaft. Thisrotatable knob adjusts the protruding amount to deploy the cuttingblade. The single vertical cutter has a pair of tool attachment endportions and a cutting blade extending in a loop between the attachmentends. The cutting blade is inclined vertically relative to alongitudinal axis of a cylinder or tube into which the attachment endsslide into. The cutting blade has a cutting edge, a portion of whichwhen extended free of the cylinder or tube extends a distance above thetube outside diameter. The cutting edge when pushed inwardly and pulledoutwardly scrapes and cuts the disc material, and when retracteddeflects into the cylinder or tube for insertion or extraction into orfrom the disc space. The vertical cutting tool further comprises a pushpull knob fixed to the rotatable knob to cut inwardly and outwardlyparallel to the tube or cylinder longitudinal axis.

The vertical cutter of the present invention allows for the method ofpreparing a void space between adjacent vertebrae for placing a fusionimplant device comprises the steps of locating a position on the patientto make an incision; cutting the tissue at the location by making asmall incision; placing an outer guide tube having an inside diameterinto the incision; inserting a cutting tool with a retracted cuttingblade inside a tube sized to pass through the inside diameter of theguide tube while having the cutter stowed internally; extending the tooltube past the guide tube directed toward a disc space; protracting thecutting blade free of the tool tube while orienting the cutting bladevertically up or down relative to a longitudinal axis of the tool tubeand wherein the protracted cutting blade has a loop shape with aninclined cutting edge extending several mm above or below the tube;cutting away disc tissue directed at one vertebrae to form a void spaceby pushing and pulling the tool in an axial direction; scraping thecutting blade along the exposed bone surfaces of the adjacent vertebraethereby removing an outer layer or layers of bone tissue and laterallyinclining the guide tool left or right slightly to widen the void space;turning the tool 180 degrees to repeat the steps of cutting away disctissue and scraping bone layers of the other vertebra to complete thevoid space; and retracting the cutting blade and withdrawing the cuttingtool.

The method can further include a step of retracting the cutting bladeprior to turning the tool 180 degrees. The method wherein the cuttingedge has a flat portion extending at least 3 mm above the tool tube andthe tool tube has an outside diameter of 8 mm. The method wherein thecutting edge can cut disc tissue and vertebral bone to form a totalmaximum void space height over 14 mm, 7 mm upwardly and 7 mm downwardlybetween two adjacent vertebrae. The method wherein the cutting blade canbe partially refracted to cut at lower heights.

DEFINITIONS

As used herein and in the claims:

A “curette” is a surgical instrument designed for scraping or debridingbiological tissue or debris in a biopsy, excision, or cleaningprocedure. In form, the curette is a small hand tool, often similar inshape to a stylus; at the tip of the curette is a small scoop, hook, orgouge.

A “rongeur” is a strongly constructed instrument with a sharp-edged,scoop-shaped tip, used for gouging out bone.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described by way of example and with reference tothe accompanying drawings in which:

FIG. 1 is a perspective view of the cutter tool assembly of the presentinvention.

FIG. 1A is an exploded view of the tool assembly of FIG. 1.

FIG. 2A is a plan view of the tooling tube.

FIG. 2B is side plan view of the internal shaft.

FIG. 3 is a plan side view illustrating the rotatable retraction andprotraction knob for moving the cutter blade of the cutting tool intoand out of the tooling tube.

FIG. 4 is a perspective view of the cutting blade of the presentinvention as formed.

FIG. 4A is a plan view of the cutting blade, the dashed linesrepresenting the sheet from which the cutting blade can be formed.

FIG. 4B is a top view of the cutting blade as formed.

FIG. 4C is a partial view taken along lines A-A of FIG. 4B showing oneportion of the cutting blade, the opposite portion having been removed.

FIG. 4D is an end view of the cutting blade illustrating the verticalelevation of the cutting blade relative to the attachment portions.

FIG. 5 is a perspective view showing the cutting blade protracted andextending outward from the tooling tube.

FIG. 6 is a side perspective view showing the cutting blade protractedrelative to the tooling tube.

FIG. 7 is a side view showing a portion of the cutting blade withdimensions from the attachment knob to the vertical elevation above theattachment means.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIGS. 1 and 1A, the cutting tool device 100 of thepresent invention is illustrated. The device 100 includes a detachablevertical cutter 10, a tool tube 102, a rotatable retraction andprotraction knob 120 and a push pull knob 130 to provide linear cuttingcapability as the tool 100 is pushed and pulled inward between twovertebral bodies to remove disc tissue and to scrape the bone exposedend plate surfaces.

With reference to FIG. 1A, further illustrated internal to the tool tube102 is a shaft 112. The shaft 112 provides a way to attach the verticalcutter 10. As further illustrated in FIG. 2A, the tube 102 has a “T”shaped end 104 that is adapted to fit in the rotatable knob 120 asillustrated in FIG. 3. The “T” shaped end 104 has a knob 120 mountedthereabout so that the knob 120 can rotate without rotating the tube102. The knob 120 has internal threads 122 adapted to engage the threads110 of the shaft 112 as illustrated in FIG. 2B. The combination ofthreads 110, 122 are designed so the shaft can be pulled or pushedaxially along the longitudinal axis of the tool by the rotation of theknob 120 best illustrated in FIG. 3. A slot is provided in the tool inFIG. 3 exposing the threads 110 of the shaft 112. The threads 110 can bemoved between positions 105 and 103 or further if so desired. This openwindow 106 provides a means for the surgeon to see the amount of travelthat the vertical cutter 10 is making relative to the tool tube 102 whenit is positioned inside the vertebral bodies. The shaft 112 has a flatend 116 to which the knob 130 is fixed.

With particular reference to the detachable vertical cutter 10, asillustrated in FIGS. 4 through 7, the vertical cutter 10 has attachmentends 12 and 14 with an opening 11 that will conveniently fit on theattachment location 114 of the shaft 112. The openings 11 are orientedat 90 degrees to attachment locations 114. The attachment locations 114are positioned on each side of the shaft 112 such that when the verticalcutter 10 is mounted on the attachment shaft 112 and pulled inside thetube 102 it securely holds the vertical cutter 10 in position so that itcan be pulled internally within the tube 102. As illustrated in FIG. 4A,the vertical cutter 10 was formed as a single piece, preferably ofshaped memory alloy material such as Nitinol wherein the material wascut from a blank sheet approximately 0.5 mm thick. The blank sheet isillustrated by dashed lines in FIG. 4A. As shown, the attachment ends 12and 14 are at the extremes of this sheet where the cutting blade 20 isinterposed between the attachment ends 12, 14. As shown, the width W_(B)is approximately 2 mm in the exemplary embodiment. Punched through theattachment ends 12, 14 are the attachment holes 11 as illustrated. Thecutting blade width W_(B) is substantially uniform across the cuttingblade 20, however may be slightly narrower at a flat portion 25. Theflat portion 25 extends about 3 mm in length. When the shaped memoryalloy material is formed into the desired cutting blade shape which isof a general oval nature as illustrated in the top view of FIG. 4B, theflat portion 25 will be at the very peak of the vertically inclinedcutting blade 20. As shown, the cutting blade sides 22 and 24 areinclined relative to the attachment ends 12, 14 and are offset slightlylower than the center line of the attachment ends 12, 14. This enablesthe cutting blade 20 when bent in the configuration shown in FIG. 4B totake the shape as illustrated. The cutting blade sides 22, 24 extendwidthwise a distance W_(T) of approximately 10.5 mm in this exemplaryembodiment to form a large oval with a flat top.

As illustrated in FIG. 4C, the blade side portion 22 on the attachmentend 12 is shown, the other side of the cutting blade 20 has the endportion 24 and 14 (not illustrated) similarly inclined. An acute angleis shown of approximately θ relative to a horizontal plane which can bevaried dependent on the length and the amount of height required.However, it is believed important that the angle θ be less than 45degrees preferably less than 30 degrees as illustrated.

With reference to FIG. 4D, the cutting blade portion 20 has the sides 24and 22 shown inclined to the flat portion 25 inclined and raised upwardrelative to the attachment ends 12, 14 to the flat portion 25. Again, aspreviously mentioned, the width of the cutting blade 20 is ofsubstantially uniform thickness W_(B) of about 2 mm and has a cuttingedge that is also generally uniform in thickness of 0.5 mm or less. Thisprovides a substantially strong and yet flexible blade 20 such that itcan be retracted and pulled inside the tube 102. This attachment of thevertical cutter 10 is illustrated in FIG. 5 where the thickness of theblade 20 is illustrated as dimension t. In the exemplary vertical cutter10, t was about 0.5 mm.

With reference to FIG. 6, the vertical cutter 10 is also shown in theprotracted position where it is free of the tool tube 102. The tool tube102 has an outside diameter OD of approximately 8 mm in this exemplaryembodiment with an inside diameter of 6.85 mm. The width of theattachment ends 12, 14 is slightly less than the 6.85 mm such that theycan slide inwardly to be attached to the shaft 112 at the attachmentlocations 114. The vertical cutter 10, when attached, has a verticaldistance from the axis of rotation, this is called the cutting traveldistance CT or cutting travel from the axis and it approximately 7.3 mmin the exemplary embodiment. This means that the cutting blade 20extends above the outside diameter of the tool tube 102 by a distance ofapproximately 3.3 mm. It is important to note that this distance CVextending vertically above or below the tube 102 on an inclination, asshown, is achieved when the cutting blade 20 is free from the tube 102.As shown, the cutting blade 20 will extend vertically upward relative tothe axis in such a fashion that the flat end 25 cutting edge can reach amaximum level of 7.3 mm in height to the vertebrae surface above it.This allows the cutting blade 20 to cut not only into the disc material,both the nucleus pulposus and the annulus fibrosus, but also to be ableto scrape along the interior surface of the vertebral plate. Thevertebral plate must be remembered to be somewhat of a saucer shapeturned upside down wherein the edges conform inwardly slightly while theinner portion of the vertebral plate is raised in a flattened elevateddome shape. This is important in that the cutting blade 20 is designedto be able to scrape not only the disc material, but also the thinlayers of this end plate of the vertebral body. By scraping it,microfractures occur and improved bone surface preparation can beachieved for a fusion implant device. As shown, the flat portion 25 hasa width of approximately 3 mm or greater. This enables the device to bepushed and pulled into and out of the disc space without any rotationalcutting. All cutting is achieved by linear action and to widen this voidspace required for the implant it is important to remember that onesimply can grab the outer tube 200 that has been inserted into a smallincision at the direct location and tilt it laterally slightly left orslightly right on a very small inclination. This allows the cuttingblade 20 to move slightly laterally and continued pushing and pullingcan create a void space approximately 10 to 15 mm for an implant 9 mmwide if so desired. The cutting blade 20 can be held in a slightlyretracted position if lowered cutting heights are need. So on initialcutting, the cutting blade 20 can be slightly retracted and pushed andpulled to cut some material away and then continue to be pushed andpulled in a fully retracted condition due to the flexibility of thecutting blade 20, it will simply scrape along the bones outer edgeremoving a thin layer and also provide a good planar surface to receivethe fusion implant device.

FIG. 7 is a similar view to that of FIG. 6 only showing a side view andonly one portion of the blade 20. It is important to note that since thecutting blade 20 is made in a looped configuration, having a somewhatoval shape flattened at the peak, it provides a substantial amount ofwidth for cutting as the entire cutting edge 21 is on a slight inclinemeaning that the side surface and the top of the blade 20 form anangulation such that only the edge 21 of the cutting surface is doingthe primary cutting, therefore there is no need for a very sharp razoredged blade. This blade 20 will cut at the edge 21 of the width andthickness performing a scraping action to remove both the disc materialand the layers of bone material needed to be removed in preparation ofthe void space.

This cutting tool 100, as illustrated, with the vertical cutter 10provides a unique way of removing disc material and preparing twoadjacent vertebrae for receiving any spinal fusion implant device. Thesurgeon will simply locate a position on the patient's back to make anend incision. The surgeon cuts the tissue at the location by making asmall incision and inserting a solid tapered dilator to allow insertionof an outer guide tube 200 that will hold the tool tube 102 portion ofthe tool 100. This outer tube 200 is illustrated in FIG. 7. This tube200 is then placed into the small incision in the desired location andinserted partially therein. This tube 200 will have an outside diameterof approximately 9.2 mm when using a tool tube 102 having an outsidediameter of 8 mm. This means that the outer tube 200 has an insidediameter of approximately slightly greater than 8 mm so that the tooltube 102 can slide freely in and out of this outer sheathing or guidetube 200. As illustrated, the surgeon will insert the cutting tool 100with the retracted vertical cutter 10 inside the tool tube 102 which hasbeen sized to pass through the inside diameter of the guide tube 200while having the cutting blade 10 stowed internally. The surgeon willuse the outer tube 200 to space the adjacent vertebral bodies whereinthe disc material is intended to be removed. This spacing of thevertebrae allows the tool tube 102 to slide inward to the disc materialand extending past the guide tube 200 directly towards or into the discspace. At this point the surgeon protracts the vertical cutter 10 byrotating the knob 120. As the cutting blade 20 extends past the tooltube 102 it will be moved into a free position and the shaped memoryalloy cutting blade 20 will return to its free and unrestrainedcondition. As such the blade 20 will then extend above the inner tube byapproximately 3.3 mm as discussed. When this occurs, the surgeon canthen push and pull on the cutting blade 10 creating a void surface byremoving the disc tissue. This includes the nucleus pulposus and theannulus fibrosus of the disc. Once this is removed the surgeon cancontinue to remove disc material by tilting on a slight lateralangulation, the entire guide tube 200 and tool 100 inside on a veryslight angle using a lateral movement. This increases the width that canbe cut such that the flat edge 25 can create a void space of at least 10to 15 mm wide to receive the fusion implant device of 9 mm. Once thishas occurred, the surgeon can continue to scrape on the exposed endplate of the vertebral body. By doing this, he or she will create cracksand fissures that will improve the osteoinductivity of the bone materialadjacent the implant. This will accelerate the fusion of the boneimplant and accelerate the healing time.

In order to cut the opposite adjacent vertebral body disc material, thesurgeon can either retract if so desired or simply rotate the tool 100such that it lines up with a vertical downward extension if he haspreviously cut in a vertical upward position. By extending the tool 100in a downward direction he can now cut the lower vertebral body disctissue above it and prepare that space by repeating the procedure in apush pull manner completing all the cutting without any requirement forrotational cutting of disc material. In this way, a chamber or voidspace that is basically rectilinear and ideally suited for receiving aspinal implant device is formed. Once all the material has been cut awayand the end plates have been scraped, the device can be retracted andpulled out of the guide tube 200 such that an implant device can bepositioned through the guide tube 200 to complete the procedure. Whilevarious dimensions have been mentioned for the exemplary embodiment,these dimensions can be varied using the concepts taught herein and willstill be within the scope of the present invention.

Variations in the present invention are possible in light of thedescription of it provided herein. While certain representativeembodiments and details have been shown for the purpose of illustratingthe subject invention, it will be apparent to those skilled in this artthat various changes and modifications can be made therein withoutdeparting from the scope of the subject invention. It is, therefore, tobe understood that changes can be made in the particular embodimentsdescribed, which will be within the full intended scope of the inventionas defined by the following appended claims.

What is claimed is:
 1. A detachable vertical cutter for insertion into acylinder or tube comprises: a single blade having a pair of toolattachment end portions and a cutting blade extending in a loop betweenthe attachment ends; and wherein the cutting blade is inclinedvertically relative to a longitudinal axis of a cylinder or tube intowhich the attachment ends slide into, the cutting blade having a cuttingedge, a portion of which when extended free of the cylinder or tubeextends a distance above the tube outside diameter, the cutting edgewhen pushed inwardly and pulled outwardly scrapes and cuts the discmaterial, and when retracted deflects into the cylinder or tube forinsertion or extraction into or from the disc space.
 2. The detachablevertical cutter of claim 1 wherein the blade is cut from a flat sheet ofshaped memory alloy and heat set to form the loop.
 3. The detachablevertical cutter of claim 2 wherein the sheet has a nominal thickness of0.5 mm or greater.
 4. The detachable vertical cutter of claim 3 whereinthe cutting blade has a nominal width of 2.0 mm or greater.
 5. Thedetachable vertical cutter of claim 3 wherein the cutting edges are theinclined outer edges at the intersection of the thickness and the width.6. The detachable vertical cutter of claim 1 wherein the cutting bladehas curved opposing sides spanning a nominal maximum between oppositesides distance of 10.5 mm or greater.
 7. The detachable vertical cutterof claim 6 wherein the cutting blade when withdrawn into the tube orcylinder bends or deflects the curved opposing sides of the cuttingblade to fit the inside diameter as well as lowering or bending theflattened end vertical inclination to slide into the tube or cylinder.8. The detachable vertical cutter of claim 6 wherein the cutting bladehas flattened distal end portion between the two curved sides along avertical cutting peak extending at least 3 mm.
 9. The detachablevertical cutter of claim 8 wherein the cutting blade is configured tofit into a 7 mm to less than 10 mm tube or cylinder having a nominaloutside diameter of 8 mm to 11 mm.
 10. The detachable vertical cutter ofclaim 9 wherein the vertical inclination of the cutting blade extends atleast 2 mm or greater above the outside diameter of the tube when thecutting blade is extended free of the tube.
 11. A vertical cutting toolcomprises: a shaft to which a cutting blade can be attached at one endand externally threaded at an opposite end; a hollow tube or cylinderfor receiving the shaft internally; a rotatable knob affixed to thehollow tube and rotatable independent of the tube or cylinder, the knobhaving internal threads to engage the threads of the shaft; a singledetachable vertical cutter having a pair of tool attachment end portionsand a cutting blade extending in a loop between the attachment ends; andwherein the cutting blade is inclined vertically relative to alongitudinal axis of a cylinder or tube into which the attachment endsslide into, the cutting blade having a cutting edge, a portion of whichwhen extended free of the cylinder or tube extends a distance above thetube outside diameter, the cutting edge when pushed inwardly and pulledoutwardly scrapes and cuts the disc material, and when retracteddeflects into the cylinder or tube for insertion or extraction into orfrom the disc space.
 12. The vertical cutting tool of claim 11 whereinthe blade is cut from a flat sheet of shaped memory alloy and heat setto form the loop.
 13. The vertical cutting tool of claim 12 wherein thesheet has a nominal thickness of 0.5 mm or greater.
 14. The verticalcutting tool of claim 13 wherein the cutting blade has a nominal widthof 2.0 mm or greater.
 15. The vertical cutting tool of claim 13 whereinthe cutting edges are the inclined outer edges at the intersection ofthe thickness and the width.
 16. The vertical cutting tool of claim 11wherein the cutting blade has curved opposite side spanning a nominalmaximum between opposite sides distance of 10.5 mm or greater.
 17. Thevertical cutting tool of claim 16 wherein the cutting blade whenwithdrawn into the tube or cylinder bends or deflects the curved sidesof the loop to fit the inside diameter as well as lowering or bendingthe flattened end vertical inclination to slide into the tube orcylinder.
 18. The vertical cutting tool of claim 16 wherein the cuttingblade has flattened distal end portion between the two curved sidesalong a vertical cutting peak extending at least 3 mm.
 19. The verticalcutting tool of claim 18 wherein the cutting blade is configured to fitinto a 7 mm to less than 10 mm tube or cylinder having a nominal outsidediameter of 8 mm to 11 mm.
 20. The vertical cutting tool of claim 19wherein the vertical inclination extends at least 3 mm or greater abovethe outside diameter of the tube when the cutting blade is extended freeof the tube.
 21. The vertical cutting tool of claim 11 further comprisesa push pull knob fixed to the rotatable knob to cut inwardly andoutwardly parallel to the tube or cylinder longitudinal axis.
 22. Amethod of preparing a void space between adjacent vertebrae for placinga fusion implant device comprises the steps of: locating a position onthe patient to make an incision; cutting the tissue at the location bymaking a small incision; placing an outer guide tube having an insidediameter into the incision; inserting a cutting tool with a retractedcutting blade inside a tube sized to pass through the inside diameter ofthe guide tube while having the cutter stowed internally; extending thetool tube past the guide tube directed toward a disc space; protractingthe cutting blade free of the tool tube while orienting the cuttingblade vertically up or down relative to a longitudinal axis of the tooltube and wherein the protracted cutting blade has a loop shape with aninclined cutting edge extending several mm above or below the tube;cutting away disc tissue directed at one vertebra to form a void spaceby pushing and pulling the tool in an axial direction; scraping thecutting blade along the exposed bone surfaces of the adjacent vertebrathereby removing an outer layer or layers of bone tissue and laterallyinclining the guide tool left or right slightly to widen the void space;turning the tool 180 degrees to repeat the steps of cutting away disctissue and scraping bone layers of the other vertebra to complete thevoid space; and retracting the cutting blade and withdrawing the cuttingtool.
 23. The method of claim 22 wherein the method of rotating the toolcan further include a step of retracting the cutting blade prior toturning the tool 180 degrees.
 24. The method of claim 22 wherein thecutting edge has a flat portion extending at least 3 mm above the tooltube and the tool tube has an outside diameter of 8 mm.
 25. The methodof claim 24 wherein the cutting edge can cut disc tissue and vertebralbone to form a total maximum void space height over 14 mm, 7 mm upwardlyand 7 mm downwardly between two adjacent vertebrae.
 26. The method ofclaim 22 wherein the cutting blade can be partially retracted to cut atlower heights.